Very short introduction of Linux

Linux is an operating system originally developed by Linus Torvalds in 90’s for cloning the Unix operating system to personal computers (PCs). It is now one of the world-renowned software projects developed and managed by the open-source community.

With its open nature in software development, free in (re-)distribution, and many features inherited directly from Unix, the Linux system provides an ideal and affordable environment for software development and scientific computation. It is why Linux is widely used in most of scientific computing systems nowadays.

Architecture

The figure above illustrates a simplified view of the Linux architecture. From inside out, the core of the system is called the kernel. It interacts with hardware devices, and provides upper layer components with low-level functions that hide complexity of, for example, arranging concurrent accesses to hardware. The shell is an interface to the kernel. It takes commands from user (or application) and executes kernel’s functions accordingly. Applications are generally refer to system utilities providing advanced functionalities of the operating system, such as the tool cp for copying files.

File and process

Everything in Linux is either a file or a process.

A process in Linux refers to an executing program identified by an unique process identifier (PID). Processes are internally managed by the Linux kernel for the access to hardware resources (e.g. CPU, memory etc.).

In most of cases, a file in Linux is a collection of data. They are created by users using text editors, running compilers etc. Hardware devices are also represented as files in the Linux.

Linux distributions

Nowadays Linux is made available as a collection of selected software packages based around the Linux kernel. It is the so-called Linux distribution. As of today, different Linux distributions are available on the market, each addresses the need of certain user community.

In the HPC cluster at DCCN, we use the CentOS Linux distribution. It is a well-maintained distribution developed closely with RedHat, a company providing commercial Linux distribution and support. It is also widely used in many scientific computing systems in the world.